cxl: Prevent adapter reset if an active context exists
This patch prevents resetting the cxl adapter via sysfs in presence of
one or more active cxl_context on it. This protects against an
unrecoverable error caused by PSL owning a dirty cache line even after
reset and host tries to touch the same cache line. In case a force reset
of the card is required irrespective of any active contexts, the int
value -1 can be stored in the 'reset' sysfs attribute of the card.
The patch introduces a new atomic_t member named contexts_num inside
struct cxl that holds the number of active context attached to the card
, which is checked against '0' before proceeding with the reset. To
prevent against a race condition where a context is activated just after
reset check is performed, the contexts_num is atomically set to '-1'
after reset-check to indicate that no more contexts can be activated on
the card anymore.
Before activating a context we atomically test if contexts_num is
non-negative and if so, increment its value by one. In case the value of
contexts_num is negative then it indicates that the card is about to be
reset and context activation is error-ed out at that point.
Fixes: 62fa19d4b4
("cxl: Add ability to reset the card")
Cc: stable@vger.kernel.org # v4.0+
Acked-by: Frederic Barrat <fbarrat@linux.vnet.ibm.com>
Reviewed-by: Andrew Donnellan <andrew.donnellan@au1.ibm.com>
Signed-off-by: Vaibhav Jain <vaibhav@linux.vnet.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
This commit is contained in:
parent
65bc3ece84
commit
70b565bbdb
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@ -220,8 +220,11 @@ What: /sys/class/cxl/<card>/reset
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Date: October 2014
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Contact: linuxppc-dev@lists.ozlabs.org
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Description: write only
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Writing 1 will issue a PERST to card which may cause the card
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to reload the FPGA depending on load_image_on_perst.
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Writing 1 will issue a PERST to card provided there are no
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contexts active on any one of the card AFUs. This may cause
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the card to reload the FPGA depending on load_image_on_perst.
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Writing -1 will do a force PERST irrespective of any active
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contexts on the card AFUs.
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Users: https://github.com/ibm-capi/libcxl
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What: /sys/class/cxl/<card>/perst_reloads_same_image (not in a guest)
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@ -229,6 +229,14 @@ int cxl_start_context(struct cxl_context *ctx, u64 wed,
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if (ctx->status == STARTED)
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goto out; /* already started */
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/*
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* Increment the mapped context count for adapter. This also checks
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* if adapter_context_lock is taken.
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*/
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rc = cxl_adapter_context_get(ctx->afu->adapter);
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if (rc)
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goto out;
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if (task) {
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ctx->pid = get_task_pid(task, PIDTYPE_PID);
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ctx->glpid = get_task_pid(task->group_leader, PIDTYPE_PID);
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@ -240,6 +248,7 @@ int cxl_start_context(struct cxl_context *ctx, u64 wed,
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if ((rc = cxl_ops->attach_process(ctx, kernel, wed, 0))) {
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put_pid(ctx->pid);
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cxl_adapter_context_put(ctx->afu->adapter);
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cxl_ctx_put();
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goto out;
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}
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@ -238,6 +238,9 @@ int __detach_context(struct cxl_context *ctx)
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put_pid(ctx->glpid);
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cxl_ctx_put();
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/* Decrease the attached context count on the adapter */
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cxl_adapter_context_put(ctx->afu->adapter);
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return 0;
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}
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@ -618,6 +618,14 @@ struct cxl {
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bool perst_select_user;
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bool perst_same_image;
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bool psl_timebase_synced;
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/*
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* number of contexts mapped on to this card. Possible values are:
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* >0: Number of contexts mapped and new one can be mapped.
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* 0: No active contexts and new ones can be mapped.
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* -1: No contexts mapped and new ones cannot be mapped.
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*/
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atomic_t contexts_num;
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};
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int cxl_pci_alloc_one_irq(struct cxl *adapter);
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@ -944,4 +952,20 @@ bool cxl_pci_is_vphb_device(struct pci_dev *dev);
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/* decode AFU error bits in the PSL register PSL_SERR_An */
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void cxl_afu_decode_psl_serr(struct cxl_afu *afu, u64 serr);
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/*
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* Increments the number of attached contexts on an adapter.
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* In case an adapter_context_lock is taken the return -EBUSY.
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*/
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int cxl_adapter_context_get(struct cxl *adapter);
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/* Decrements the number of attached contexts on an adapter */
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void cxl_adapter_context_put(struct cxl *adapter);
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/* If no active contexts then prevents contexts from being attached */
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int cxl_adapter_context_lock(struct cxl *adapter);
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/* Unlock the contexts-lock if taken. Warn and force unlock otherwise */
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void cxl_adapter_context_unlock(struct cxl *adapter);
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#endif
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@ -205,11 +205,22 @@ static long afu_ioctl_start_work(struct cxl_context *ctx,
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ctx->pid = get_task_pid(current, PIDTYPE_PID);
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ctx->glpid = get_task_pid(current->group_leader, PIDTYPE_PID);
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/*
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* Increment the mapped context count for adapter. This also checks
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* if adapter_context_lock is taken.
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*/
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rc = cxl_adapter_context_get(ctx->afu->adapter);
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if (rc) {
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afu_release_irqs(ctx, ctx);
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goto out;
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}
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trace_cxl_attach(ctx, work.work_element_descriptor, work.num_interrupts, amr);
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if ((rc = cxl_ops->attach_process(ctx, false, work.work_element_descriptor,
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amr))) {
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afu_release_irqs(ctx, ctx);
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cxl_adapter_context_put(ctx->afu->adapter);
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goto out;
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}
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@ -1152,6 +1152,9 @@ struct cxl *cxl_guest_init_adapter(struct device_node *np, struct platform_devic
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if ((rc = cxl_sysfs_adapter_add(adapter)))
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goto err_put1;
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/* release the context lock as the adapter is configured */
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cxl_adapter_context_unlock(adapter);
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return adapter;
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err_put1:
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@ -243,8 +243,10 @@ struct cxl *cxl_alloc_adapter(void)
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if (dev_set_name(&adapter->dev, "card%i", adapter->adapter_num))
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goto err2;
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return adapter;
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/* start with context lock taken */
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atomic_set(&adapter->contexts_num, -1);
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return adapter;
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err2:
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cxl_remove_adapter_nr(adapter);
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err1:
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@ -286,6 +288,44 @@ int cxl_afu_select_best_mode(struct cxl_afu *afu)
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return 0;
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}
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int cxl_adapter_context_get(struct cxl *adapter)
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{
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int rc;
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rc = atomic_inc_unless_negative(&adapter->contexts_num);
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return rc >= 0 ? 0 : -EBUSY;
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}
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void cxl_adapter_context_put(struct cxl *adapter)
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{
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atomic_dec_if_positive(&adapter->contexts_num);
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}
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int cxl_adapter_context_lock(struct cxl *adapter)
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{
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int rc;
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/* no active contexts -> contexts_num == 0 */
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rc = atomic_cmpxchg(&adapter->contexts_num, 0, -1);
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return rc ? -EBUSY : 0;
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}
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void cxl_adapter_context_unlock(struct cxl *adapter)
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{
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int val = atomic_cmpxchg(&adapter->contexts_num, -1, 0);
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/*
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* contexts lock taken -> contexts_num == -1
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* If not true then show a warning and force reset the lock.
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* This will happen when context_unlock was requested without
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* doing a context_lock.
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*/
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if (val != -1) {
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atomic_set(&adapter->contexts_num, 0);
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WARN(1, "Adapter context unlocked with %d active contexts",
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val);
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}
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}
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static int __init init_cxl(void)
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{
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int rc = 0;
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@ -1487,6 +1487,8 @@ static int cxl_configure_adapter(struct cxl *adapter, struct pci_dev *dev)
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if ((rc = cxl_native_register_psl_err_irq(adapter)))
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goto err;
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/* Release the context lock as adapter is configured */
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cxl_adapter_context_unlock(adapter);
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return 0;
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err:
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@ -75,12 +75,31 @@ static ssize_t reset_adapter_store(struct device *device,
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int val;
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rc = sscanf(buf, "%i", &val);
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if ((rc != 1) || (val != 1))
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if ((rc != 1) || (val != 1 && val != -1))
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return -EINVAL;
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if ((rc = cxl_ops->adapter_reset(adapter)))
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return rc;
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return count;
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/*
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* See if we can lock the context mapping that's only allowed
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* when there are no contexts attached to the adapter. Once
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* taken this will also prevent any context from getting activated.
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*/
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if (val == 1) {
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rc = cxl_adapter_context_lock(adapter);
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if (rc)
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goto out;
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rc = cxl_ops->adapter_reset(adapter);
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/* In case reset failed release context lock */
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if (rc)
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cxl_adapter_context_unlock(adapter);
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} else if (val == -1) {
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/* Perform a forced adapter reset */
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rc = cxl_ops->adapter_reset(adapter);
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}
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out:
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return rc ? rc : count;
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}
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static ssize_t load_image_on_perst_show(struct device *device,
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